Windows: Add support for PerMonitorV2 DPI awareness

Add support for opting in to PerMonitorV2 DPI awareness
on the command line:
	-platform windows:dpiawareness=3

This mode is supported on Windows 10 and up. Setting it
requires using the new SetProcessDpiAwarenessContext
API, which can be resolved from user32.dll.

Task-number: QTBUG-68712
Change-Id: I37821e27a67e08c2e9fef25e494cfd7abed13314
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 14 insertions, 5 deletions

diff --git a/src/plugins/platforms/windows/qwindowsintegration.cpp b/src/plugins/platforms/windows/qwindowsintegration.cpp
index 74e6985980..ed401bac30 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.cpp
+++ b/src/plugins/platforms/windows/qwindowsintegration.cpp
@@ -219,7 +219,7 @@ static inline unsigned parseOptions(const QStringList &paramList,
             options |= QWindowsIntegration::DontPassOsMouseEventsSynthesizedFromTouch;
         } else if (parseIntOption(param, QLatin1String("verbose"), 0, INT_MAX, &QWindowsContext::verbose)
             || parseIntOption(param, QLatin1String("tabletabsoluterange"), 0, INT_MAX, tabletAbsoluteRange)
-            || parseIntOption(param, QLatin1String("dpiawareness"), QtWindows::ProcessDpiUnaware, QtWindows::ProcessPerMonitorDpiAware, dpiAwareness)) {
+            || parseIntOption(param, QLatin1String("dpiawareness"), QtWindows::ProcessDpiUnaware, QtWindows::ProcessPerMonitorV2DpiAware, dpiAwareness)) {
         } else if (param == u"menus=native") {
             options |= QWindowsIntegration::AlwaysUseNativeMenus;
         } else if (param == u"menus=none") {
@@ -263,10 +263,19 @@ void QWindowsIntegrationPrivate::parseOptions(QWindowsIntegration *q, const QStr
 
     if (!dpiAwarenessSet) { // Set only once in case of repeated instantiations of QGuiApplication.
         if (!QCoreApplication::testAttribute(Qt::AA_PluginApplication)) {
-            m_context.setProcessDpiAwareness(dpiAwareness);
-            qCDebug(lcQpaWindows)
-                << __FUNCTION__ << "DpiAwareness=" << dpiAwareness
-                << "effective process DPI awareness=" << QWindowsContext::processDpiAwareness();
+
+            // DpiAwareV2 requires using new API
+            bool hasDpiAwarenessContext = QWindowsContext::user32dll.setProcessDpiAwarenessContext != nullptr;
+            if (dpiAwareness == QtWindows::ProcessPerMonitorV2DpiAware && hasDpiAwarenessContext) {
+                m_context.setProcessDpiV2Awareness();
+                qCDebug(lcQpaWindows)
+                    << __FUNCTION__ << "DpiAwareness: DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2";
+            } else {
+                m_context.setProcessDpiAwareness(dpiAwareness);
+                qCDebug(lcQpaWindows)
+                    << __FUNCTION__ << "DpiAwareness=" << dpiAwareness
+                    << "effective process DPI awareness=" << QWindowsContext::processDpiAwareness();
+            }
         }
         dpiAwarenessSet = true;
     }